This invention relates to highly reflective, highly durable, retroreflective and reflective sheeting constructions which preferably comprise a layer of pressure sensitive adhesive (containing an organofunctional coupling agent) adjacent a specular reflective layer.
A number of retroreflective and reflective sheeting products have been marketed, e.g., for use in road signs, advertising signs, conspicuity sheeting, etc. A typical example of a retroreflective sheeting is characterized by a single layer of tiny transparent microspheres embedded in a thermoset polymeric bead bond layer which is backed by an optional transparent spacing layer and a specularly reflective layer and an adhesive. One such sheeting is known as xe2x80x9cenclosed-lensxe2x80x9dsheeting and was first taught by Palmquist, U.S. Pat. No. 2,407,680, which is herein incorporated by reference. Other such sheeting are described in U.S. Pat. Nos. 4,664,966 (Bailey) and 4,721,649 (Belisle), which are herein incorporated by reference. Such sheeting has been sold commercially for many years in large volume and to the general satisfaction of its users.
Despite this general satisfaction, there has been a desire for an improvement in certain properties of the sheeting. For example, it is sometimes desired to produce retroreflective sheeting which is cleanly removable from a substrate. Traffic control, safety identification and delineation, or commercial advertising uses of reflective sheetings have inherent costs for the materials and the labor required in the initial applications. Should these initial applications require modification or changes over time due to new traffic laws or safety conditions, expiration of intended use or warranties, or new trends in advertising and consumer awareness, the replacement and environmental costs often compound considerably with each renewed application. Additional material and labor costs must be expended to expose, clean, resurface, or replace the substrate. These procedures not only consume time and obvious resources, but also involve considerable energy use, may produce undesired volatile emissions, and produce waste disposal problems.
It would be highly desirable to provide sheeting that is cleanly removable from a substrate and which may be removed at low cost.
The present invention provides improved and novel removable sheeting, having a specular reflective layer, and a pressure sensitive adhesive layer adjacent the specular reflective layer. The adhesive layer of this sheeting includes an organofunctional coupling agent. In preferred embodiments the sheeting is retroreflective and further includes an array of retroreflective elements.
The retroreflective sheeting of the present invention has improved removability properties over the retroreflective sheeting of the prior art. Suitable removable sheetings of the present invention are capable of a broad range of temporary (typically less than two years of intended application before removal) to permanent (i.e., long term applications spanning several years) adhesion properties. Suitable sheetings include a pressure sensitive adhesive layer containing an organofunctional coupling agent (e.g., an organofunctional silane compound) adjacent a specular reflective layer. The-adhesive system preferably forms an integral and inseparable structure on the sheeting, whereby clean and complete post application removal is possible, preferably even after long periods of time or climatic exposure. When used on retroreflective sheeting, the sheeting to substrate adhesion values are preferably such to resist environmental, aging, and pressure washing forces.
In preferred embodiments, only simple hand peel forces are required to continuously remove a reflective sheeting. As a result, replacement programs experience significant cost and environmental advantages. More preferably, the surface of a substrate is exposed and unharmed to its original finish in a minimum of time and with little effort. Heat or cold shock treatments, scrapping utensils, solvent or cleaning fluid applications, and manpower and energy investments to remove the sheeting or adhesive residue are preferably no longer required. Also avoided or eliminated as being unnecessary are finish restoration by-products and wastes such as solvents, cleaning fluids, contaminated containers and rags. Repainting due to scratched or degraded finishes is also avoided.
The sheeting of the present invention may be used to form a wide variety of articles, including, for example, retroreflective identification and signage for temporary markings (e.g., construction work zones and detour routes), retroreflective and reflective identification sheeting for use on vehicles (e.g., decals on police or fire vehicles and die cut alpha-numerics removed from pre-applied reflective license plates), retroreflective and reflective identification and advertising sheeting for use on vehicles (e.g., commuter buses, taxi cabs, delivery trucks, and heavy and long vehicles and their trailers), retroreflective and reflective advertising sheeting for stationary applications (e.g., store fronts, mail and package drop boxes, and real estate for sale signs).